Hearing and Speech

• pinna 


  collects the sound and amplifies it
• auditory canal

  1. links outer and middle ear 

  2. transmits sound waves into the skull
• tympanic membrane 


  converts soundwaves into physical vibrations in the membrane (eardum)
• ossicles


  malleus (hammer), incus (anvil), stapes (stirrup)
• function of ossicles 


  transmit vibrations from the tympanic membrane to the inner ear
• eustachian tube 


  links back of nose to middle ear
• Eustachian tube 


  equalises pressure differences between middle ear and external environment
• inner ear


  where physical vibrations are converted into nerve signals
• membraneous labyrinth 


  system of fluid-filled chambers and channels
• vestibular system 


  provides us with a sense of balance and spatial awareness
• semi-circular canals 


  detect rotation
• otolith organs


  linear acceleration
• endolymph 


  fluid in the semi-lunar canals that flows when the head is moved
• crista ampullaris


  responsible for translating flow of endolymph to nerve signals
• excessive triggering of crista ampullaris


  motion sickness
• otholith organs - urticle 


  detects horizontal movement
• otholith organs - saccule 


  detects verticle acceleration
• macula 


  patch of sensitive hair cells, enclosed in a gelatinous layer
• scala vestibuli 


  connected to the oval window and the stapes
• scala tympani 


  connected to round window which opens the middle ear
• helicotrema


  connects scala tympani to scala vestibuli
• scala media 


  between vestibular and tympanic canals, connected to the saccule
• organ of corti 


  lined with internal and external hairs and sends axons to the cochlear nerve and hence to the brain via VIII auditory
• basilar membrane


  sound waves cause it to stimulate the hair cells